Vibration damper assemblies are used in a clutch disc for a motor vehicle power train where torsional vibration of the connected elements become troublesome in causing disturbing noises in the transmission and driveline. The vibration damper assembly is interposed in the clutch disc ahead of a manually operated transmission to neutralize the torsional vibrations emanating from the vehicle engine. A vibration damper may also be utilized for a lock-up clutch inserted in a torque converter for an automatic transmission where the vibrations occurring during direct drive between the torque input and the drive shaft would not be hydraulically dampened.
Conventional automotive clutch vibration dampers incorporate coil springs between the driving and driven plates of the damper. The loading characteristics of torque versus angular displacement for the coil spring dampers are linear and the spring rate can be increased in stages, which are also linear, by sequentially loading additional springs. Stress and geometrical design limitations are encountered with conventional coil spring designs in applications requiring large angular displacements and high torque capacity and with spring rate requirements that vary depending on operating conditions. The present invention acts to overcome these problems in providing a damper having a non-linear spring rate.
The present invention comprehends the provision of a vibration damper assembly for a clutch disc providing a non-linear spring rate. The non-linear rate is accomplished by substituting a bowed leaf spring pack for each coil spring set in the damper assembly. Loading tests on a bowed leaf spring pack under various magnitudes of radial compression provided non-linear load versus deflection characteristics. A wide range of design flexibility is available in shaping the load-deflection curve depnding on the spring pack design and the amount of radial compression.
The present invention also comprehends the provision of a non-linear spring rate vibration damper providing a load versus deflection curve having a decreasing spring rate at higher loading conditions, which is not obtainable with sequential linear spring systems. The decreasing spring rate at the higher loading conditions is desirable for vibration problems occurring under certain drive conditions.
The present invention further comprehends the provision of a non-linear spring rate vibration damper which is not subject to the wear and notching effects in a coil spring design damper. Coil spring designs are subjected to wear and notching effects at the coil ends due to the corner loading scissors action occurring at the spring retainer windows of the drive plates. This type of wear is completely eliminated with the bowed leaf spring type of design.
Another object of the present invention is the provision of a clutch vibration damper assembly wherein the damper has one or more leaf springs at each spring retainer window. Additional springs are stacked in a pack to obtain increased torque capacity. If additional damping is required, elastic material may be bonded between the leaf springs.
A further object of the present invention is the provision of a clutch vibration damper assembly where angular and parallel misalignment can be accommodated with the same bowed leaf spring type of design used for the power transmission coupling applications. Also, no lubrication is required for the leaf spring damper assembly.
Further objects are to provide a construction of maximum simplicity, efficiency, economy and ease of assembly and operation, and such further objects, advantages and capabilities as will later more fully appear and are inherently possessed thereby.